1. Field of the Invention
The present invention relates to an aqueous dispersion for chemical mechanical polishing. More specifically, the present invention relates to an aqueous dispersion that is useful when soft interlayer insulating films with a small elastic modulus are used in chemical mechanical polishing (hereunder referred to as “CMP”) of wiring pattern-formed wafers during the manufacture of semiconductor devices.
2. Prior Art
Aqueous dispersions comprising inorganic particles of colloidal silica, colloidal alumina or the like have been commonly used in the prior art as polishing agents for CMP of working films and interlayer insulating films during the manufacture of semiconductor devices. However, since such aqueous dispersions have low dispersion stability and tend to aggregate, scratches are generated on polishing surfaces by aggregated masses, and this results in lower yields. In order to solve this problem there have been proposed various methods including (1) uniform dispersion using a homogenizer and (2) removal of the aggregated masses with a filter. However, these methods fail to improve the polishing agents themselves, while also introducing new problems such as a lower polishing rate.
In recent years, more attention is being focused on achieving lower permittivities of interlayer insulation films for the purpose of improving VLSI performance. Lower permittivities have been achieved by the development of interlayer insulation films comprising, in place of SiO2 films with high permittivities, silsesquioxane (permittivity: approximately 2.6–3.0), fluorine-containing SiO2 (permittivity: approximately 3.3–3.5), polyimide-based resins (permittivity: approximately 2.4–3.6, trade name “PIQ” by Hitachi Chemical Industries Co., Ltd.; trade name “FLARE” by Allied Signal Corp., and the like), benzocyclobutene (permittivity: approximately 2.7, trade name “BCB” by Dow Chemical Corp., and the like.), hydrogen-containing SOG (permittivity: approximately 2.5–3.5) and organic SOG (permittivity: approximately 2.9, trade name “HSGR7” by Hitachi Chemical Industries Co., Ltd.) and the like. However, because these insulating films have low mechanical strength and are soft and brittle compared to SiO2 films, they sometimes produce large scratches with such conventional aqueous dispersions comprising inorganic particles. Numerous scratches of various shapes are also produced in some cases.